fix(pilot): replace pydantic EmailStr with str+regex (email-validator dep missing → backend startup ImportError → deploy unhealthy)

Root cause: PR #330 SF-B3 introduced pydantic EmailStr import in
backend/app/api/v1/pilot.py at module level. EmailStr requires the
email-validator package which is not in pyproject deps, so backend import
crashed:

  pydantic.errors.PydanticImportError: `email-validator` is not installed

Result: backend container started but uvicorn import failed → /health
endpoint never bound → docker-compose marked container unhealthy → deploy
exited 1.

Fix: drop EmailStr, use plain `str | None` with a minimal regex pattern.
Strict email validation can run on the frontend or CRM side.

backend/app/api/v1/pilot.py

@@ -11,7 +11,7 @@ import logging
 from typing import Annotated, Any, Literal
 
 from fastapi import APIRouter, Depends, Request
-from pydantic import BaseModel, EmailStr, Field
+from pydantic import BaseModel, Field
 from sqlalchemy import text
 from sqlalchemy.orm import Session
 
@@ -25,7 +25,10 @@ router = APIRouter()
 class PilotRequestInput(BaseModel):
     name: str = Field(min_length=2, max_length=200)
     phone: str | None = Field(default=None, max_length=50)
-    email: EmailStr | None = None
+    # Note: was EmailStr but `email-validator` package not in deps → ImportError
+    # on backend startup → container unhealthy → whole deploy fails. Using plain
+    # str + minimal regex; full validation can happen on frontend/CRM side.
+    email: str | None = Field(default=None, max_length=200, pattern=r"^[^@\s]+@[^@\s]+\.[^@\s]+$")
     company: str | None = Field(default=None, max_length=200)
     message: str | None = Field(default=None, max_length=2000)
     source: Literal["landing", "analyze_page", "other"] = "landing"